Graphical Construction: Drawing a circle tangent to other circles

An actual problem solved. The build of wire making a coil

Tonight’s post is a graphical construction that does not have a built-in function in CAD. Drawing circles tangent to other circles was an actual problem I had to “go back to the books” to solve a problem. The picture to the left is a drawing I created trying to determine the diameter of a coil of wire forming a solenoid.

However, this problem is very common in the design of things. The example I use in the video is designing a gear train knowing the pitch diameter of the gears. (The pitch diameter is the point of contact of the gears.)